Contact



C. L. HARVEY Aug. 18, 1953 CONTACT Filed May 16, 1951 LILJLILILILL IE ZIll! l aivluunu INVENTOR. 6'50/4 Z. Ham E) Patented Aug. 18, 1953 SATESATNT "FFICE CONTACT tion of Pennsylvania Application May l'fi, 1951,Serial No. 226,693

invention relates are composed of a sintered combination of a highlyconductive metal such as copper or silver and a semirefractory or arefractory metal, such as tungsten, tungsten carbide, molybdenum, andmolybdenum carbide. The final treatment of the initially porous sinteredcombination comprises the operation of impregnating the same with a highconductivity metal, such as silver. The electrical contacts referred toherein contain, in most cases, about forty'or more percent of therefractory material.

Electrical contacts which contain refra t y material in an amount of theorder of that referred to above are hard and brittle, and hence cannotbe subjected to the usual forming operations such as rolling, slitting,cutting, punching, coining and staking. Therefore, they are furnished asindividually molded and treated pieces which have not heretofore beenavailable in other than individual form. This is a highly objectionablefeature of these contacts when attempting to utilize them in a highproduction rate set-up. This is particularly true when the individualcontacts are very small.

It is presently the practice to either braze or weld the contact to thecontact arm. In applying these contacts to the contact carrying arm theoperator feeds the contact in position in a jig in the welding machineand then applies the arm to which the contact is to be welded to thecontact.

In many instances the contact is of the order of in diameter and inthickness and is accordingly not easily manipulated into its position.

Moreover, there is considerable risk to the operator whose hands mustfor an instant while placing the contact in place be underneath theelectrode which is shortly thereafter to be machine operated withconsiderable force against the arm and contact while applying currentfor welding.

In order to overcome these difiicultiesit has been proposed to bond theindividual contacts to a paper strip with an adhesive. However, afterremoval of the contact from the paper strip it is found that theadhesive adheres to the contact 5 Claims. (Cl. 200-166) and adverselyaffects its characteristic or presents special problems in removal ofthe adhesive or other foreign matter prior to the securement of thecontact on the contact arm.

In accordance with my present invention, I have discovered that I canachieve a binding between adjacent contacts so as to form a l stripcomprising a plurality of such contacts. Such a long strip of contactsnow makes it relatively easy to handle the operations of feedinindividual contacts into the welding jig. he operator, in such aconstruction, merely holds the contact strip at one end and uses thecontact strip to position an end contact into the weldin ig.

Accordingly, an object of my invention is to provide a novel means forconnecting a plurality of electrical contacts toegther in series and anovel method for obtaining this result.

A further object of my invention is to provide a bonding material whichwill have no deleterious effect upon the conductivity or otherproperties of the electrical contacts.

A further object of my invention is to combine the bonding operationwith a previously established operation in the production of electricalcontacts.

To carry this out, a further object of my invention is to utilize thecontact briquette impregnating metal as the bonding material so that theoperation of impregnating the contacts will also result in connectingthem.

A further object of my invention is to provide a bonding materialbetween the contacts which may easily be ruptured to allow separationbetween two adjacent contacts, but which material is sufiiciently strongmechanically to maintain the connection until it is affirmativelybroken.

My novel bonding process which satisfies the above objects, theconnected series of contacts being produced thereby, may more easily beunderstood by referring to the following description and drawings inwhich Figure 1 is a side view of a series of contacts prior to bonding.

Figure 2 is a side view of a series of contacts bonded together.

Figures 3 and 4 show plan and side views of the severed contact.

There are several methods by which it is possible to produce the kind ofcontacts or parts contemplated in this disclosure; these parts beingmade from metal powders by what is commonly referred to as theimpregnation process. A1-

der consisting of a conductive metal, this metal.

being preferably identical to that which will subsequently be used toimpregnate the contact, as for example, silver. This. combination isthoroughly mixed, as for example. by. usilng;. a, tumbling process. Thepowders thus mixed are then inserted into a die cavity of an appropriatesize and shape, and compacted'therein'by'apply ing pressure to the dieplungers which-1 compact the powder. Thereafter' the compacted materialis. sintered. The compacting pressure is soselected that the briquettewhich is. obtained will havea predetermined percent porosity after it.is sintered subsequent to the compacting opera.- tion.

Theprocess is thencompleted by placing an appropriate quantity of theimpregnating ma.- terial, as for instance, silver, upontheporoussintered. compact, and placing the whole, within a furnace andbringing said whole to a temperature in excess ofthemelting point of theimpregnating. material. The. impregnating material when thus. meltedwill flow into. the sintered compact and fill the voids, creating adense product.v

In connection with this general description. of the methodused tovproduce the electrical contacts. of. the type. to. which this. inventionis die rected, I will here describe may. novel bonding operation.

As shownin Figure 1, after the. contacts 1 are pressed. and sintered,they are placed upon a support 2, and so positioned that they are,adjacent to and touching each other, and so arranged that. their centerslie along a predetermined path, in. this case said, path being astraigl'itv line indicated by axis line 33. An appropriate size slug 4of the impregnating material isthenplaced upon each of the compacts i.It is to, be. noted that. the individual slugs 4 of saidimpregnatingmaterial maybe replaced. by a bar or; rodof any desirableshape, said bar being of sufiicient length to rest upon thetops of all.the combined contacts.

The above, mentioned assembly is-then placed intoa furnace which is heldat a temperature sufficient, to melt the impregnating. material andcause itto now and impregnate the, contacts.

Inaddition to impregnating the contacts 1, as heretofore mentioned, theimpregnating metal will form .a fillet 5 between any two adjacent,contacts]. as shown in Figure 2; one contact being bondedby this. fillet5 between the...t,w,o contacts tadjacent tov it.

Thus, the bonding operation has. been combined with the normallyrequired impregnating process, this process heretofore beingoutlined.

Thebonding fillet l is. thus produced with a relatively soft material,namely theimpregnating. metal, suchas. silver or copper. The fillet,

being soft, may easily be rupturedby-an-operator, or. bymechanicalmeans.- associatedwith a positioning fixture. However, the fillet issufficiently strong so that a strip of a predetermined length, supportedhorizontally or vertically by one end, will be capable of supporting itsown weight. Since the fillet is composed of the impregnating material,it must necessarily be a good conductor, and hence cannot adverselyafiect the propertiesbf.the-contact.

I wi l ow be ppar nt-from the above description that when a stripcontaining a plurality of such contacts I bonded to each other at theirtangential engaging point 5 is applied to a reeeptable or jig in awelding machine, a simple roekingmovement oi; the strip while thecontact isheldginplace. in; the jig will release the strip fm-this-cpntact; at the tangential point where the contact is secured tothe next adjacent end contact:

appropriate fixture and jig for the positioning of the contacts can beconstructed or modified so as to utilize the heretofore describedcombined form of electrical contacts rather than the individual items.It is obvious thatjthere is greater ease in both mechanical and manualhandling of the combined form than there is with the. individualcontacts.

A jig and fixture combination is conceivable which may better utilize acombined form of'el ectrical contacts in and annular ring rather thanthe aforementioned strip form. Hence I'wi'shmy invention to cover anyshape into which a; plurality of contacts may be formed by my'novelmethod.

While I have described my invention in connection with a particularcomposition of an electrical contact, it will now be'obvious that myinvention is applicable to. any contact which, can be joined togetheratian, appropriate point to form a.v strip of a plurality of contacts;Accordingly, I prefer to be bound not by the specific disclosures hereincontained, but only by the appended. claims.

I claim:

1..A strip oi silver impregnated.electrical'con tacts; adjacent,contacts being connected by silver fillets.

2. A strip. of electrical contacts impregnated witha conducting metal;adjacent contacts being connected'byfillet's of said impregnating,metal.

3. A strip. of initially porous electrical; con tacts impregnated with aconducting metal; adjacent contacts being connected by fillets .of'tlieimpregnating metal.

4. A strip of initially porous electrical cont ts. impr nated. with aconducting. me al; a jacent. contacts being connected by fillets of theimpregnatingmetal, each. fillet, extending in tegrally from within onecon act. into. an d'- jacent contact.

5.. A strip of conductin powder imp nat d electrical. contacts; adjacentcontacts being connected by said conducting powder fillets.

CECIL L. HARVEY.

References Cited in the file of. this patent UNITED. STATES PATENTS-Number Name Date 2,181,083. Fayette Nov; 21, 19.39 2,433,687 Durst Dec.30, 19.47 2,458,552 Blattner Jan. 11,. 19.49 2,501,164 Durstvv Mar. 21,.1950

1. A STRIP OF SILVER IMPREGNATED ELECTRICAL CONTACTS; ADJACENT CONTACTSBEING CONNECTED BY SILVER FILLETS.